The first one you found looks fine to me. The bank's XML is very straightforward and doing your own implementation or using the helper you linked would both be pretty trivial.

The only problems are that (a) it only updates once a day and (b) as a free service it's presented as-is, and if one day it gives you some off numbers and you use them to make a transaction and get burned you don't have any recourse. You may not even have any recourse with the $10/mo one, but I imagine you do get a reasonable guarantee with the expensive one.

I don't know that (a) is a practical concern in most cases, but wars, coups, terrorist attacks, and Apple product unveilings presumably can change economic differentials pretty rapidly.